BU-604: How to Process Data from a “Smart” Battery

Even though smart batteries have been in service since the mid-1990s, they still behave much like a “black box” and do not communicate to the outside world. Device manufacturers continue to mandate that the battery be replaced on a date stamp rather than refer to the more relevant FCC information contained in the battery. Expensive packs are thus discarded every 2–3 years instead of utilizing the full 5-year life expectancy of Li-ion.

A new frontier is opening that provides easy battery information. The Battery Parser (by Cadex) does this by establishing communications between the user and the battery by fetching intrinsic battery data to reveal state-of-function (SoF). The Fishbowl icon as shown in Figure 1 consists of the Charge Ring indicating state-of-charge and the Status Dome with PASS, CHARGE, CHECK, and FAIL messages. The Status Dome also illustrates the energy storage capability together with Battery Fade that moves towards the Pass/Fail line with usage and age.

PASS indicates sufficient capacity and SoC CHARGE requires charging before use as SoC slipped below the Charge Alarm. CHECK includes cell imbalance, high Max Error, elevated internal resistance and more. FAIL hints at capacity fade, exceeding calendar date or passing beyond pre-set cycle count.

Battery status indicators must separate state-of-charge and capacity and treat them as unrelated entities. While a battery with low SoC can be recharged, capacity loss is permanent and predicts end-of-life. This condition is demonstrated with the encroaching black ceiling bar on top of the Fishbowl. Pressing the Status Dome on a device featuring a touchscreen reveals possible deficiencies, as well as information relating to the battery model, specifications, serial number and manufacturing date. The Fishbowl settings can be altered by the user.

Storing the battery test results in a cloud-based database enables an overview of the entire battery fleet in terms of location, application, performance and service requirements. This is made possible with the availability of the serial number and manufacturing date in a smart battery. To check batteries needing replacement, the operator simply calls up packs that have dropped below the 80 percent capacity or are older than, say, 5 years.

The operator can also verify SoC by listing all batteries with less than 10 percent reserve before charging. Tight reserve could lead to failure during heavy traffic or in an emergency. If consistently low, the pass/fail target capacity threshold should be set higher to boost the reserve. If, on the other hand, most batteries return with 40 percent capacity after a long mission or a full day, then the target capacity can be lowered without affecting reliability.

The Battery Parser finds a sweet spot between reliability and economy. The service life of each battery can be fully utilized and system reliability improved, reducing environmental harm and lowering operating costs. In addition, fewer devices are sent for repair because the battery becomes a controlled part.

A cost saving by using battery analysis was demonstrated in a 340-bed hospital in the USA. When the need to replace the batteries for patient monitors came to $56,000 on the date stamp method, the supervisor objected and requested that the packs be checked with a battery analyzer. This revealed that most batteries were in good condition and the budget was reduced to $11,000.

Military is another application where battery analysis will help. A modern soldier carries radios, GPS devices, smartphones, night vision goggles, infrared sights, flashlights and counter-IED equipment. This amounts to roughly seven battery types, of which 10 packs are needed each for a 72-hour mission at a weight of about 9kg (20 lb) per solider. Batteries have become the second highest expense next to munitions. This can be reduced with a maintenance program, without which soldiers are soon carrying rocks instead of batteries as Figure 2 demonstrates.

Maintenance keeps deadwood out of the military arsenal. The digital state-of-health of “smart” batteries can be verified within seconds or recorded during each charge.

Other uses for the Battery Parser are drones and robots. Drones are demanding on the battery as heavy loads result in a shorter than expected cycle life. Battery maintenance is paramount to prevent an expensive vehicle from crashing should a second landing approach be necessary. (See also BU-504: How to Verify Sufficient Battery Capacity)

Battery maintenance utilizing the Battery Parser is best placed into the battery charger. Such a system shows the capacity with each charge. Alternatively, a quick insertion reveals the battery status before use. Knowing the performance of each battery enables planning a mission according to the available energy source, reducing unscheduled events.

Wireless connectivity to the cloud permits collective battery management in which each charge updates the information. This provides one of the most transparent battery management systems possible without added logistics. Battery status can be shown on a PC or smartphone with the click of a finger.

Smart batteries and chargers with performance evaluation further assist to classify batteries into performance groups: A-grade batteries with a capacity of 90–100 percent can be reserved for critical missions, B-grade packs with 80–90 percent are for everyday use, and the C-grade with 70–80 percent may be kept as spares or used for shorter errands. Having full control of the battery fleet improves reliability, simplifies logistics and protects the environment as each battery can be utilized for their full service life.

References

[1] Courtesy: Cadex Electronics